One of the historical election landmarks last year had nothing to do with race or the presidency. Rather, it had to do with pigs and chickens — and with overarching ideas about the limits of human dominion over other species.

Fred R. Conrad/The New York Times

Nicholas D. Kristof

I’m referring to the stunning passage in California, by nearly a 2-to-1 majority, of an animal rights ballot initiative that will ban factory farms from keeping calves, pregnant hogs or egg-laying hens in tiny pens or cages in which they can’t stretch out or turn around. It was an element of a broad push in Europe and America alike to grant increasing legal protections to animals.

Spain is moving to grant basic legal rights to apes. In the United States, law schools are offering courses on animal rights, fast-food restaurants including Burger King are working with animal rights groups to ease the plight of hogs and chickens in factory farms and the Humane Society of the United States is preparing to push new legislation to extend the California protections to other states.

At one level, this movement on behalf of oppressed farm animals is emotional, driven by sympathy at photos of forlorn pigs or veal calves kept in tiny pens. Yet the movement is also the product of a deep intellectual ferment pioneered by the Princeton scholar Peter Singer.

Professor Singer wrote a landmark article in 1973 for The New York Review of Books and later expanded it into a 1975 book, “Animal Liberation.” That book helped yank academic philosophy back from a dreary foray into linguistics and pushed it to confront such fascinating questions of applied ethics as: What are our moral obligations to pigs?

John Maynard Keynes wrote that ideas, “both when they are right and when they are wrong, are more powerful than is commonly understood. Indeed the world is ruled by little else.” This idea popularized by Professor Singer — that we have ethical obligations that transcend our species — is one whose time appears to have come.

“There’s some growth in numbers of vegetarians, but the bigger thing is a broad acceptance of the idea that animals count,” Mr. Singer reflected the other day.

What we’re seeing now is an interesting moral moment: a grass-roots effort by members of one species to promote the welfare of others. Legislation is playing a role, with Europe scheduled to phase out bare wire cages for egg production by 2012, but consumer consciences are paramount. It’s because of consumers that companies like Burger King and Hardee’s are beginning to buy pork and eggs from producers that give space to their animals.

For most of history, all of this would have been unimaginable even to people of the most refined ethical sensibility (granted, for many centuries those refined ethicists were also untroubled by slavery). A distinguished philosopher, Thomas Taylor, reacted to Mary Wollstonecraft’s 1792 call for “the rights of woman” by writing a mocking call for “the rights of brutes.” To him, it seemed as absurd that women should have rights as that animals should have rights.

One of the few exceptions was Jeremy Bentham, the philosopher who 200 years ago also advocated for women’s rights, gay rights and prison reform. He responded to Kant’s lack of interest in animals by saying: “The question is not, Can they reason? nor, Can they talk? but, Can they suffer?”

In recent years, the issue has entered the mainstream, but even for those who accept that we should try to reduce the suffering of animals, the question remains where to draw lines. I eagerly pushed Mr. Singer to find his boundaries. “Do you have any compunctions about swatting a cockroach?” I asked him.

“Not much,” he replied, citing reasons to doubt that insects are capable of much suffering. Mr. Singer is somewhat unsure about shellfish, although he mostly gives them the benefit of the doubt and tends to avoid eating them.

Free-range eggs don’t seem offensive to him, but there is the awkwardness that even wholesome egg-laying operations depend on the slaughtering of males, since a male chick is executed for every female allowed to survive and lay eggs.

I asked Mr. Singer how he would weigh human lives against animal lives, and he said that he wouldn’t favor executing a human to save any number of animals. But he added that he would be troubled by the idea of keeping one human alive by torturing 10,000 hogs to death.

These are vexing questions, and different people will answer them differently. For my part, I eat meat, but I would prefer that this practice not inflict gratuitous suffering.

Yet however we may answer these questions, there is one profound difference from past centuries: animal rights are now firmly on the mainstream ethical agenda.

The Hindu-Muslim communal violence that led to the attacks in Mumbai, as well as the warnings that the New York City transit system may have been targeted by al-Qaida, are one form of terrorism. There are other forms.

The wars in Iraq and Afghanistan, when viewed from the receiving end, are state-sponsored acts of terrorism. These wars defy every ethical and legal code that seek to determine when a nation can wage war, from Just War Theory to the statutes of international law largely put into place by the United States after World War II. These wars are criminal wars of aggression. They have left hundreds of thousands of people, who never took up arms against us, dead and seen millions driven from their homes. We have no right as a nation to debate the terms of these occupations. And an Afghan villager, burying members of his family’s wedding party after an American airstrike, understands in a way we often do not that terrorist attacks can also be unleashed from the arsenals of an imperial power.

Barack Obama’s decision to increase troop levels in Afghanistan and leave behind tens of thousands of soldiers and Marines in Iraq—he promises only to withdraw combat brigades—is a failure to rescue us from the status of a rogue nation. It codifies Bush’s “war on terror.” And the continuation of these wars will corrupt and degrade our nation just as the long and brutal occupation of Gaza and the West Bank has corrupted and degraded Israel. George W. Bush has handed Barack Obama a poisoned apple. Obama has bitten it.

The invasions and occupations of Afghanistan and Iraq were our response to feelings of vulnerability and collective humiliation after the attacks of Sept. 11, 2001. They were a way to exorcise through reciprocal violence what had been done to us.

Collective humiliation is also the driving force behind al-Qaida and most terrorist groups. Osama bin Laden cites the Sykes-Picot Agreement, which led to the carving up of the Ottoman Empire, as the beginning of Arab humiliation. He attacks the agreement for dividing the Muslim world into “fragments.” He rails against the presence of American troops on the soil of his native Saudi Arabia. The dark motivations of Islamic extremists mirror our own.

Robert Pape in “Dying to Win: The Strategic Logic of Suicide Terrorism,” found that most suicide bombers are members of communities that feel humiliated by genuine or perceived occupation. Almost every major suicide-terrorist campaign—over 95 percent—carried out attacks to drive out an occupying power. This was true in Lebanon, Sri Lanka, Chechnya and Kashmir, as well as Israel and the Palestinian territories. The large number of Saudis among the 9/11 hijackers appears to support this finding.

A militant who phoned an Indian TV station from the Jewish center in Mumbai during the recent siege offered to talk with the government for the release of hostages. He complained about army abuses in Kashmir, where ruthless violence has been used to crush a Muslim insurgency. “Ask the government to talk to us and we will release the hostages,” he said, speaking in Urdu with what sounded like a Kashmiri accent.

“Are you aware how many people have been killed in Kashmir? Are you aware how your army has killed Muslims? Are you aware how many of them have been killed in Kashmir this week?” he asked.

Terrorists, many of whom come from the middle class, support acts of indiscriminate violence not because of direct, personal affronts to their dignity, but more often for lofty, abstract ideas of national, ethnic or religious pride and the establishment of a utopian, harmonious world purged of evil. The longer the United States occupies Afghanistan and Iraq, the more these feelings of collective humiliation are aggravated and the greater the number of jihadists willing to attack American targets.

We have had tens of thousands of troops stationed in the Middle East since 1990 when Saddam Hussein invaded Kuwait. The presence of these troops is the main appeal, along with the abuse meted out to the Palestinians by Israel, of bin Laden and al-Qaida. Terrorism, as Pape wrote, “is not a supply-limited phenomenon where there are just a few hundred around the world willing to do it because they are religious fanatics. It is a demand-driven phenomenon. That is, it is driven by the presence of foreign forces on the territory that the terrorists view as their homeland. The operation in Iraq has stimulated suicide terrorism and has given suicide terrorism a new lease on life.”

The decision by the incoming Obama administration to embrace an undefined, amorphous “war on terror” will keep us locked in a war without end. This war has no clear definition of victory, unless victory means the death or capture of every terrorist on earth—an impossibility. It is a frightening death spiral. It feeds on itself. The concept of a “war on terror” is no less apocalyptic or world-purifying than the dreams and fantasies of terrorist groups like al-Qaida.

The vain effort to purify the world through force is always self-defeating. Those who insist that the world can be molded into their vision are the most susceptible to violence as antidote. The more uncertainty, fear and reality impinge on this utopian vision, the more strident, absolutist and aggressive are those who call for the eradication of “the enemy.” Immanuel Kant called absolute moral imperatives that are used to carry out immoral acts “a radical evil.” He wrote that this kind of evil was always a form of unadulterated self-love. It was the worst type of self-deception. It provided a moral façade for terror and murder. The wars in Iraq and Afghanistan are a “radical evil.”